In the field of semiconductor devices, there has recently been an increased demand for film-formation processing technology to form a desired surface. Especially, MOCVD technique has been focused as a film-formation processing technique to form a thin-film for compound semiconductors that are useful to an optical device and a high-speed electronic device. In the film-forming device used for MOCVD technique and equipped with a substrate rotating mechanism, a thin-film forming technique is particularly important to form a desired uniform thin-film obtained by the result of a certain chemical reaction made by the introduction of a reactive raw gas over the substrate surface.
When a desired thin-film is formed by the MOCVD technique, it is known that the surf ace reaction produced on the substrate surface by the reactive raw gas is extremely complicated. In other words, because a lot of parameters including temperatures of the substrate and the raw gas, flow velocity, pressure, active chemical species contained in the raw gas, components of the residual gas in the reaction system and the like contribute to the surface reaction, it is very difficult to control these parameters in the MOCVD technique to form a desired thin-film.
In this circumstance, various techniques have been proposed with respect to the film-forming device utilizing MOCVD technique, wherein a desired thin-film is formed in a more uniform and stable manner over the substrate surface under a certain condition.
As a technique to form a thin-film due to equalizing the thickness and the composition of the film, a method for rotating substrates in a horizontal plane has been adapted.
For example. Journal of Crystal Growth 115 discloses that when forming an InGaAsP thin-film arranged on an InP substrate in a lattice-shaped manner, the pressure within the reaction tube of the MOCDV apparatus and the flow rate of the carrier gas are determined merely based on the characteristic that the boundary of the film is clearly defined, and equalizing the thickness and the composition of the film formed from the upstream to the downstream of the carrier gas flow is carried out by rotating the substrates in the horizontal plane.
In the substrate rotation technique, in order to improve the effects of the equalized film thickness and film compositions by the rotation of the substrates, a so-called rotation/revolution mechanism for the substrate has been used, wherein a susceptor retaining substrates is rotated in such a manner that the substrates revolve around the rotational axis of the susceptor.
As best seen in FIG. 5, such a rotation/revolution mechanism generally comprises substrates W, substrate trays 200 for retaining substrates W, a susceptor 300 for retaining the substrate trays 200, a substrate rotation mechanism (not shown) for rotating the substrates W and a rotation shaft SC for rotating the susceptor 300.
For example, as one example of a prior art film-forming device with a substrate rotating mechanism, Japanese Patent Publication No. Hei-7-78276 discloses a rotating device which is equipped with a rotating susceptor utilizing for a vapor-phase epitaxy chamber. The rotating device is equipped with a flat susceptor, which rotates around a rotation shaft perpendicular to the reference plans in a manner parallel to the reference plane, a stabling means for stabling the susceptor to be supported floatingly and a rotating means for rotating the susceptor. Further, both of the stabling means and the rotating means are formed by the susceptor, the rotation shaft, and structures arranged at the reference plane, which cooperate to each other by the influence of one or more gas flow. In order to obtain a rotational movement of the susceptor to be supported floatingly by the viscous force, the rotating device for the vapor-phase epitaxy reactor chamber is constituted such that the structures at the reference plane are provided with a hole and spiral grooves for the insertion of a supplemental gas flow, and the gas flow supplied through the hole is flown into the grooves curving toward the direction to which the susceptor is rotated.
Japanese Laid-open Patent Publication No. Hei-10-116789 discloses a substrate rotating device, wherein substrates are rotated within the chamber which is constituted by walls forming a cavity. The substrate rotating device comprises a first rotating means arranged within the cavity and rotating the substrate around a first axis, a second rotating means arranged outside of the chamber and rotating a planetary gear around the first axis, a magnetically coupling means magnetically coupling the first rotating means and the second rotating means through the walls and harmonically rotating the first and second rotating means around the first axis, a sun gear arranged outside of the chamber and meshing with the planetary gear, and a first driving means carrying out a first rotation with respect to the first rotating means, the second rotating means and the substrate around the center axis and further simultaneously carrying out, by the meshing between the planetary gear and the sun gear, a second rotation with respect to the first rotating means, the second rotating means and the substrate around the first axis.
Japanese Laid-open Patent Publication No. 2000-91232 discloses a substrate heating and transporting process apparatus. The substrate heating and transporting process apparatus comprises a pressure-controllable common chamber, a transporting plate movable in the common chamber while retaining a vacuum state, one or more substrate heating section transported by the transporting plate, and one or more pressure-controllable processing chamber connected to the common chamber through the opening of the separation wall. The substrate heating section includes a heating means and a substrate tray which holds a substrate to be heated by the heating means. The substrate heating section abuts to the opening of the separation wall, while retaining a certain substrate temperatures with a downward movement thereof by the movement of the transporting plate so that the substrate heating section and the processing chamber are locked to form a vacuum-sealed chamber that is independently pressure-controlled by the substrate heating section and the processing chamber.
Further, Japanese Laid-open Patent Publication No. 2000-87237 discloses a coaxial-type vacuum heating apparatus. The vacuum heating apparatus comprises a pressure-controllable common chamber, a cylindrical revolutionary moving shaft carrying out rotational and vertical movements while retaining a vacuum state in the common chamber and connecting with electric wiring and water-cooling piping, both positioned outside of the common chamber, a transporting plate coaxially fixed to the rotating axis of the revolutionary moving shaft, one or more substrate heating section arranged at a position around the rotating axis of the transporting plate, and one or more pressure-controllable processing chamber connected to the common chamber through the opening of the separation wall in association with the substrate heating section, wherein the substrate heating section includes a heating means having water-cooling piping for the purpose of water cooling, and a substrate tray holding a substrate to be heated by the heating means.
However, these prior art substrate rotating mechanisms have the following drawbacks:                (1) Since the susceptor is rotated in such a manner that the rotation of the rotation driving section causes the rotation shaft, which is arranged at a position of the center axis of the susceptor provided with a substrate tray holding a substrate, to be rotated, the susceptor has to be highly accurately attached with respect to the rotation shaft. This leads to a difficulty in adapting large-sized substrates.        (2) These substrate rotating mechanisms have a relatively complicated construction because of the rotation shaft. Therefore, at a periodic inspection of the MOCVD apparatus having the aforementioned substrate rotating mechanism, removing the susceptor requires relatively complicated and time-consuming operations.        (3) As illustrated in FIG. 5, since the rotation shaft is normally provided at the center of the susceptor and also at the center of the reacting chamber, a temperature control mechanism is not positioned on the extension of the axis line extending through the center of the reacting chamber. For this reason, it is difficult to control the temperature around the center portion of the reacting chamber.        (4) At a periodic inspection of the MOCVD apparatus, fixing the susceptor to the original position after removing and cleaning the susceptor is relatively complicated and time-consuming, and precisely positioning the susceptor, especially detecting the horizontal plane is complicated. If a small error occurs in the proximity of the center of the susceptor during the positioning operation, a relatively large error occurs at the outer periphery of the susceptor.        
(5) When the substrate rotating mechanism rotates the substrate by injecting a gas toward the reverse side of the substrate, a foreign object, such as a deposit caused by a part of reaction products, is subject to be whirled up at the substrate tray and its periphery by the injection of the gas, resulting in a deposit or adhesion of the foreign object at the reverse side and the front side of the substrate.                (6) In the substrate rotating mechanism in which a gas is injected toward the reverse side of the substrate, a film-forming process is carried out with the film-formation plane of the substrate positioned upward. In this event, a foreign object dropping from the above tends to deposit on the film-formation plane. Further, in such a substrate rotating mechanism wherein injection of the gas is carried out, it is difficult to check whether the substrate is rotated normally.        (7) In the film-forming processing device with such a substrate rotating mechanism, since the susceptor is formed from a continuous disk-shaped member, it is difficult to make a desired temperature profile on the susceptor by the temperature control mechanism during the film-forming process.        
In view of the above, the purpose of the present invention is to provide a film-forming device with a substrate rotating mechanism, wherein with the provision of the rotation/revolution mechanism of the substrate, a precise adjustment of the rotation shaft of the susceptor is carried out with a simple manner, an excellent maintainability is achieved and further a deposit of the foreign object on the substrate is prevented, and wherein with making the temperatures of the susceptor and the periphery of the substrate to be a desired temperature profile, a desired film-forming process having a desired film property and a desired film thickness can be carried out.